The present invention relates generally to the field of radiation shielding equipment, and more particularly, to shields for use by radio-pharmacists while withdrawing aliquots of radioactive materials contained within shielded vials.
It has long been known to shield syringes containing radioactive materials. Heretofore, such syringes have been shielded by devices which generally surround the syringe barrel, while permitting the needle and needle hub of the syringe to extend beyond the end of the shield. Means have been provided in these shields for holding the syringe more or less securely within the shield. Some syringe shields have incorporated a high density glass to facilitate viewing of the syringe markings and contents. In U.S. Pat. No. 3,820,541 a shield for a hypodermic syringe is disclosed which is lead lined and is provided with a bayonet fitting element engaging the manually engaged end of the syringe. A coil spring cooperates with the bayonet fitting element to prevent wobbling between the barrel of the syringe and the barrel of the shield. The barrel of the shield is so configured that a small end of the barrel of the syringe is uncovered to permit visual inspection of flow to and from the syringe.
In U.S. Pat. No. 4,062,353 dated Dec. 13, 1977 a syringe shield is disclosed which is characterized in the provision of a removable, arcuately shaped bushing positionable in the bore of the shield for decreasing the effective diameter thereof to support a syringe barrel against a single set screw. The bushing is inserted with the syringe barrel into an oversized bore in the shield permitting passage of the needle of the syringe with an intact needle cover, thereby maintaining the sterility of the needle.
While most prior art syringe shields provide good finger and hand protection from the radiation coming from within the syringe, such shields normally offer little or no protection from the radiation coming from the mouth of the vial from which the radioactive material is drawn. Even though most such vials are fitted with vial shields, when the covers of those shields are removed and the vial inverted for dosage withdrawal, little or no protection is provided against radiation emanating from the mouth of the dosage vial. Further, since most dosage vials contain multiple dosages of radioactive materials, it may readily be appreciated that the amount of radiation emanating from a dosage vial is normally many times greater than that emanating from a syringe containing a single dosage of the subject material. Further, in view of the orientation of the dosage vial during withdrawal of the radioactive material, the radiation emanating from the dosage vial normally extends over a much greater area of the hand than that emanating from the subject syringe.
The high density viewing glass of state of the art syringe shields tends to be easily broken and/or dislodged from its setting in the syringe shield barrel. These windows normally project from the exterior surface of these syringe shields, and thus are particularly prone to breakage, etc. Finally, a thick viewing glass makes observation of the volumetric markings on a syringe disposed within the shield difficult to read, particularly against a metallic background which is often the color of the oxides of lead or tungsten.
According to state-of-the-art methods, it is desirable to measure and calibrate the radioactive dosage of an aliquot which has been withdrawn from a dosage vial into the syringe, prior to the injection of that material into a patient. This is normally accomplished by inserting the loaded syringe (without syringe shield) into a dose calibrator which measures the amount of radioactivity contained within the syringe. Since most radio-pharmacists are acutely aware that their total radiation exposure is as dependent upon the time of exposure as it is upon the intensity of that exposure, most radio-pharmacists prefer to work quickly with radioactive materials. Since state of the art syringe shields, even if used during the withdrawal of material from the dosage vial, must be removed in order to calibrate dosage, many radio-pharmacists omit the use of any syringe shield, at least until after calibration has been completed.